There is so much information here, that I'm not sure I followed it all - so I hope I have some of it straight, enough to make the following opinion anyway:
1) Call the Humane Ass'n again, tell them you have personally witnessed these animals without FOOD and WATER - in temperatures above 90 degrees and worse. You've witnessed them tied out in the sun. You've witnessed the owners out of town, and the animals without any caregivers. You have VIDEO. Tell them you want these animals confiscated. Tell them you've previously contacted them. Tell them if the animals are not taken from the home, you'll forward the video to the ASPCA and the HSUS with a letter informing them that your local Humane Assn' is doing nothing. I mean....I don't understand how they'd do nothing - I've never experienced that ever...
2) If the HA still does nothing - if it were me, and their lives were in danger - I'd go get those animals myself and bring them to a private rescue group.
Sorry you're going through this - these people sound awful. Good luck, and bless you for doing something. Keep us posted.